Needle-Punched Glass Mat

ABSTRACT

The invention relates to a mat made of needle-punched strands comprising a strand made of mineral glass that has been sized by a composition comprising water, where the solids content of said composition comprises 1-30 wt % coupling agent and 30-99 wt % polyvinylpyrrolidone. The invention also relates to a method for the preparation of a mat comprising
         a) the deposition or projection of sized strands onto a moving belt to form a blanket of said strands, which is driven by said belt, then   b) the needle punching with barbed needles which pass through said blanket and move in the direction of the blanket at substantially the same speed as the blanket when they pass through it, with a punch density ranging from 1 to 25 punches per cm 2 .       

     This method is rapid and effective, and the mat obtained can be deformed easily by hand to be placed in a mold for the manufacture of a composite by the injection of resin (RTM), This mat can also be incorporated into a sheet of preimpregnated material (SMC) and be molded under pressure.

The invention relates to a novel mat of glass fibers that is usable forthe reinforcement of composite materials prepared notably by injection(so-called RTM method from the English “resin transfer molding”) orprepared from a sheet molding compound (synonymous with SMC from theEnglish sheet molding compound). One can also impregnate the mataccording to the invention directly with a thermosetting resin, notablyto prepare translucent plates, The RTM method and the method using sheetmolding compound generally use thermosetting matrixes. However, it isnot ruled out to use the mat according to the invention in the contextof the preparation of a composite with thermoplastic matrix, especiallyof the polyurethane type, notably via the RIM method (from the English“reinforced injection molding”).

Owing to the invention, the compounds prepared are particularlytranslucent, and one distinguishes no or only a few strands bytransparency in the composite.

A mat for the reinforcement of composite materials must presentpreferably the following properties:

-   -   sufficient cohesion to be windable, unwindable (storage and        transport),    -   sufficient cohesion to be cut into pieces, be held by hand, and        placed by hand into the mold (RTM),    -   not prick the hands when one handles it or places it into the        mold (RTM),    -   allow itself to be deformed easily by hand, when one places it        manually in the mold (RTM),    -   correctly preserve the shape that is imparted by hand in the        mold (RTM),    -   allow itself to be impregnated by the injection resin (RTM) or        SMC (generally of the polyester type and sometimes of the epoxy        type) in the easiest possible way,    -   present a structure that is as homogeneous as possible,        particularly without holes or another surface feature that can        cause a mark on the surface of the final product,    -   reinforce the composite as much as possible.

In addition, one wishes to manufacture it

-   -   at the greatest possible speed,    -   with the fewest possible steps, and    -   using the fewest possible chemical products (such as the        binders).

The final composite must present generally the best possible resistanceto impacts, the least possible uncontrolled porosity (no unintentionallyenclosed gas bubbles), and the best possible surface appearance, notablythe exposed edge (narrow face) of the final pieces, and it must be astransparent as possible.

WO2005/054559 teaches a method for the preparation of a mat thatcomprises

a) the deposition or projection of fibers on an advancing moving belt toform a blanket of said fibers, which is driven by the belt, then

b) the needle punching with barbed needles that pass through saidblanket and move in the direction of the blanket at substantially thesame speed as the blanket when they pass through it, with a punchdensity ranging from 1 to 25 punches per cm².

This method leads to mats of excellent quality for the reinforcement ofcomposite materials. However, the applicant has discovered that thenature of the sizing could influence the behavior of the mat during theneedle punching. While a standard sizing of mineral fibers (notably ofglass) can result in the breaking of the strands during the needlepunching, the sizing according to the invention protects the fibers muchbetter during needle punching, and it confers to the strand a betterflexibility and a more sliding surface, and much fewer strand ruptureshave to be deplored. The breaking of the strand during the needlepunching results in the release of airborne particles into themanufacturing workshop, discomfort during handling (it pricks thehands), and in the fact that the mat presents a less satisfactoryresistance. In addition, the reinforcing strength for the composite isreduced.

The present invention procures an improvement of the teaching ofWO2005/054559 whose content is included by reference. The technique ofdeposition of continuous strands in a blanket on a flat conveyor hasbeen described notably in U.S. Pat. No. 3,969,171 and U.S. Pat. No.4,208,000. Notably, the sizing of the glass strands has the function offacilitating the handling of said strands by these devices.Particularly, the sizing protects the strands from breaking and itpromotes the adherence of the strand to the wheels of these devices.This adherence must be neither too strong nor too weak. The strand mustnot slide too much, so that one can optimize its tension between thewheels of these devices (such as the one of FIG. 4 of U.S. Pat. No.3,936,558).

Sizing compositions containing a small quantity of polyvinylpyrrolidonehave been taught by FR2349622, U.S. Pat. No. 4,140,833, FR2413336, U.S.Pat. No. 5,038,555, U.S. Pat. No. 4,448,911, WO2005/012201.

The invention concerns first a mat of glass strands that have been sizedby a composition comprising water and whose solids content comprises1-30 wt % coupling agent and 30-99 wt % polyvinylpyrrolidone (PVP).According to the invention, one sizes the mineral strands, (notablyglass strands) with this sizing composition. The solids content of thecomposition can also comprise, in addition, 0-79 wt % lubricant (nonPVP), preferably 5-70 wt % lubricant, and even more preferably 20-70 wt% lubricant.

Notably, the coupling agent can be present in the solids content in theamount of 2-10 wt %. The PVP can especially be present in the amount of30-90 wt %. Notably, the lubricant (not of the PVP type) can be presentin the amount of 5-78 wt %.

In general, the composition (which can be used as a sizing composition)contains no epoxy resin.

The coupling agent is usually an organosilane whose function is toimprove the binding between the fibers and the matrix of the composite.Thus, it should be chosen as a function of the matrix (which isgenerally of the thermosetting type).

This organosilane also comprises at least one reactive group capable ofreacting with the surface hydroxyl groups of the mineral fibers (madenotably of glass) in such a way as to graft the modified organosilane(which is modified in that it has reacted with its reactive group andhas thus lost a part of said reactive group) to the surface of thefilaments. The organosilane that is used during the sizing is generallythe hydrolyzed derivative of an alkylsilane, itself comprising generallythe trialkoxysilane group, i.e., —Si(OR)₃, where R represents ahydrocarbon radical, such as a methyl or ethyl or propyl or butylradical. The organosilane can thus be, for example, the hydrolyzedderivative of one of the following compounds:

-   -   gamma-aminopropyltriethoxysilane    -   gamma-glycydoxypropyltrimethoxysilane    -   methacryloxypropyltrimethoxysilane (often referred to as A174).

Polyvinylpyrrolidone can have a weight-average molecular weight of6000-3,000,000, preferably 100,000-2,000,000.

The lubricant is oily to the touch. The lubricant can be chosen notablyfrom the following list:

-   -   cocotrimethylammonium chloride    -   lithium chloride    -   quaternary cationic ammonium salt    -   alkylphenolethoxylated ester (notably the Stantex FT 504 from        Cognis)    -   Arquad C35 (for example, Akzo Nobel).

The lubricant is preferably a polyethylene ester glycol (often calledPEG). Notably, it can be PEG 400 mL.

The sizing composition preferably contains, in addition, an antifoamingagent, whose content in the solids content can be 5-500 ppm by weight.

The sizing composition contains water. The quantity of water is suchthat the solids content of the composition represents 0.5-10 wt %, andpreferably 0.8-6 wt % of the composition. The applicant has discoverednotably that the content in the solids content of the sizing compositioncan be very low, for example, on the order of 0.8-2 wt %, which presentsthe advantage of causing less soiling of the operating devices.

The use of continuous strands leads to an advantage at the level of thesurface appearance and more particularly the exposed edge of the finalcomposites, and at the level of the homogeneity of the distribution ofthe fibers in the final composite. Indeed, the exposed edge of themolded pieces is much more distinct, smooth and better shaped than whencut strands are used. It seems that the use of cut strands requires thata large quantity of the ends of cut strands be located on the surface orjust below the surface of the exposed edges of pieces. The origin ofthis phenomenon is the fact that the cut strands naturally have anorientation parallel to the principal faces of the composite. Thisaccumulation of ends of cut strands at the exposed edges seems topromote the presence of porosities at the exposed edges at the beginningof the process. The bubbles formed then dilate due to the effect of thetemperature (on the order of 200° C. for the solidification of thethermosetting resin), which tends to deform the appearance of thesurface of the exposed edges. It seems that the use of continuousstrands reduces this phenomenon considerably. Indeed, instead of astrand end at the surface (when cut strands used), one would get more ofa loop of continuous strand, which goes toward a smoother surface.

For the SMC application, the mat must in addition be able to creepeasily during molding under a press. We recall that an SMC, prior tomolding, is in the form of a prepreg sheet containing a thermosettingresin, where said sheet contains in its middle a blanket ofreinforcement strands. According to the prior art, these strands aresystematically cut strands. Indeed, in the mold, the SMC is subjected toa pressure and it must creep easily to fill the entire volume of themold due to the effect of the pressure. For the person skilled in theart, this creep is possible because the strands are cut and can moveeasily with respect to each other. The SMC surface before pressing ingeneral represents only approximately 30% of the surface of the finalcomposite. There is a change from 30% to 100% due to the effect of thecompression. According to the prior art, to prepare an SMC, one projectscut strands on a moving blanket of a resin-based paste, and one depositsanother blanket of paste on top to enclose the cut strands, as in asandwich. The SMC is then wound and stored. It is unwound to cut off apiece (generally called “flap of prepreg material”) whose surfacerepresents only 30% of the surface area of the final piece, one placessaid piece into a mold, and one proceeds to hot molding under the press.The thermosetting resin hardens during this treatment. In the context ofthe present invention, one can use, instead of cut strands, continuousstrands in the context of the SMC technology. Indeed, the blanket ofcontinuous strands can creep sufficiently during the compression of theSMC. One can use the mat strands according to the invention (cut orcontinuous strands) in the context of the SMC technique. The use ofcontinuous strands of SMC additionally leads to an advantage at thelevel of the surfaces, and particularly of the exposed edges of thefinal composites. Indeed, the exposed edge of the molded pieces is muchmore distinct, smooth and better-shaped than when cut strands are used.In addition, when cut strands are used, the required creep of the SMCduring the molding leads to a preferential orientation of the strands,which can generate surface corrugations. Indeed, since the cut strandsare independent, they follow the flows too easily and orient themselvesalong the lines of flow. The strands can even agglomerate or form clumpsas a result of following these flows too much. On the other hand, thecontinuous strands resist any orientation because of their length, whilesufficiently following the expansion of the SMC during the compression.Consequently, the use of continuous strands leads to a betterhomogeneity of the reinforcement of the composite. At an identical fibercontent, the use of a continuous strand generally leads to a compositehaving a superior rigidity that is 5-12% better in comparison to the useof a cut strand.

The manufacture of a mat for the reinforcement of the composites by theRTM method generally passes through the step of deposition or projectionof freshly sized strands on a moving belt. However, the bed of strandsat this stage has no consistency and cannot be handled. It can also notbe wound or unwound, because its different layers of strands would mix.Therefore, it must be bound either chemically or mechanically.

For chemical binding, one applies a chemical binder of the thermoplasticor thermosetting type to it, generally in powder form, and one thenproceeds to a thermal treatment, which melts the thermoplastic orpolymerizes the thermosetting product, and finally, after cooling,creates bridges between the strands. However, this binder confers aspringiness effect to the structure of the mat, which then tends not tokeep less gradual shapes (for example, in the corners of the mold). Onthe other hand, there is a desire to limit the use of chemical productsin the spirit of respecting the environment. In addition, the meltingheat treatment of the thermoplastic is at a relatively high temperature(220-250° C.), which leads to a severe baking of the sizing, making thestrands and thus the mat more stiff and more difficult to deform (theglass lattice is then blocked).

To provide mechanical binding for a mat, the latter can be subjected toa conventional needle punching. However, this generally leads to thebreaking of strands, causing a lowering of the mechanical properties, aswell as to the formation of points that emerge from at least one face ofthe mat. These points then prick the hands of the handlers. In addition,since the mat advances while the needles planted in the mat are fixedhorizontally and move only vertically, this causes perforations muchlarger than the cross sections of the needles, and tends to twist theneedles. These perforations mark the surface, which is reflected insurface defects in the final piece. Indeed, these holes fill with resin,and because of the shrinkage of the resin after polymerization,depressions remain visible on the surface.

Known mats exist which comprise a central core made of curly fibers ofpolypropylene (PP) and of external layers of cut glass strands, all ofwhich are bound by a seam of synthetic wire, such as polyester (PET).The curly fiber tends to give body to the mat, to facilitate thepenetration of the resin and fill the gap of the mold (space between thetwo metal parts of the mold). However, neither the PET nor the PP fiberreinforces the composite. In addition, the seam is visible in the finalcomposite, and, moreover, the needles used for the seam cause holes atthe surface. These holes fill with resin and, because of the shrinkageof the resin after polymerization, depressions remain visible on thesurface.

According to the invention, one applies a special needle punching to themat, giving it sufficient consistency, without breaking or whilebreaking only few strands, notably because of its special sizing, andwithout formation of any excessively large holes. The mat according tothe invention is sufficiently deformable by hand at ambient temperatureand it is very permeable to the resin. According to the invention, theneedle punching is achieved with needles that move at the same time asthe mat, at substantially the same speed as the mat, in a directionparallel to the direction of displacement of the mat. In addition, thenumber of needle punches is reduced; it is at most 25 punches per cm²,preferably at most 15 punches per cm², and even more preferably at most10 punches per cm². In general, the number of needle punches is at least1 punch per cm² and preferably at least 2 punches per cm².

We recall that mats and felts differ clearly to the extent that a mat isa flat object that can be used as reinforcement, while a felt is anobject that has volume and can be used for thermal insulation. The matgenerally has a thickness of 0.8-5 mm, and more generally 1-3 mm, whilea felt is much thicker, having generally a thickness of more than 1 cm.A felt usually has a density of 85-130 kg/m³. A mat is much more dense,since its density can be on the order of 300 kg/m³. However, one doesnot express the density of a mat in terms of volume-based density, butin surface area-based density, as a flat reinforcement.

Thus, the invention relates notably to a method for the preparation of amat comprising

a) the deposition or projection of fibers on an advancing moving belt toform a blanket of said fibers, which is driven by the belt, then

b) the needle punching with barbed needles that pass through saidblanket and move in the direction of the blanket at substantially thesame speed as the blanket when they pass through it, with a punchdensity ranging from 1 to 25 punches per cm².

It is preferred for at least 1 barb and preferably 2 barbs of eachneedle to pass though the thickness of the mat at each punch. It ispreferred for the depth of penetration of the needles (length of needlesticking out of the mat after having passed through it) to be 5-20 mm.The needles preferably have a diameter (smallest circle that containsthe entire cross section of the needle including the barbs) of 0.2-3 mm,and even more preferably of 0.5-1.5 mm. Such needle punching leads to amat that can be handled, wound and unwound, and easily removed manuallyfrom the mold, and that does not prick the hand, and presents no holemarks on the surface. Due to this special needle punching, one can causethe mat to advance at high speeds, for example, at at least 2 m per min,and even at least 5 m per min, and even at least 8 m per min. Ingeneral, the speed is at most 35 or at most 30 m per min, or at most 20m per min. During the passage of the needles through the mat, strandsbecome set in the barbs and they are entrained to form loops in front ofthe mat, without rupturing the strands. These loops link the mat and caneasily be deformed while preserving the function of binder duringplacement in the mold. These loops do not prick the hands because thereis no rupture of the strands.

To achieve such needle punching, one can, for example, use certainpreliminary needle punching devices with a cylinder, which are normallydesigned to process felts made of polymer fibers, such as, for example,the machine with part number PA169 or PA1500 or PA2000 marketed byAsselin (NSC group). In this type of machine, the needles describe anelliptic movement with a horizontal component that allows the needles inthe mat to follow it in its movement.

The mat according to the invention has generally a surface area-baseddensity of 50-3000 g/m². It may be a mat with cut strands or a mat withcontinuous strands. Thus, before the needle punching, one deposits orprojects on the moving belt that advances in the direction of the needlepunching device, cut strands having generally a length of 10-600 mm, andmore particularly 12-100 mm, or continuous strands. In the case ofcontinuous strands, whose number may be 5-1200, they are projected onthe moving belt through the intermediary of an arm that oscillatestransversely with respect to the direction of advance of the belt. Forthe technique of projection of continuous strands, reference can bemade, for example, to WO 02084005. Each of the projected strands cancomprise 20-500 unit fibers (in fact, continuous filaments). It ispreferred for the strand to have a titer of 12.5-100 tex (g/km).

The material constituting the fibers (continuous filaments), and thusthe strands, is mineral, and can comprise a friable glass, such as glassE or the glass described in FR2768144 or an alkaline-resistant glasscalled AR glass, which comprises at least 5 mol % ZrO₂. Notably, the useof the glass AR leads to a mat that reinforces effectively matrices madeof cement or can reinforce thermosetting composites with matrix, whichare to come in contact with the corrosive environment. The glass canalso be free of boron. Moreover, one can also use a mixture of glassfibers and polymer fibers, such as polypropylene fibers, notably themixed fibers marketed under the trademark Twintex® by Saint-GobainVetrotex France. The strands used to produce the mat thus comprise glassfibers (filaments).

The invention also relates to a method for manufacturing a mat, whichmethod comprises the already described needle punching step. Beforeneedle punching, the cut or continuous strands are deposited orprojected onto a moving belt. At this stage, the strands can be dry,either because they come from rovings (or bobbins), or because they weredried after sizing and before the needle punching according to theinvention. However, the applicant has observed that it is advantageousfor the strands to be slightly humid to pass into the needle punchingdevice. Excessively high humidity can lead to soiling.

The mat according to the invention may be subjected to at least onedrying step, depending on the case. If the strands used are dry at thestart, and the strands are not impregnated with any liquid, the dryingis not necessary. The drying is necessary if the strands are impregnatedwith a liquid at the time of the manufacture of the mat according to theinvention. In general, the strands are freshly sized at the time oftheir use in the method according to the invention. Thus, it is possibleto dry the strands on the moving belt before the needle punching.However, as already indicated, it is preferred to preserve theimpregnated state for the needle punching, and thus it is preferred todry the sheet of strands only after the needle punching. The drying canbe carried out by passing the moving belt into an oven at a temperatureof 40-170° C., and more particularly 50-150° C. Such a thermal treatmentdoes not produce an excessively strong drying of the sizing of thestrands, which preserve flexibility intact.

The mat according to the invention can be integrated in a complexcomprising several juxtaposed layers. Notably, the mat according to theinvention, in its variant using continuous strands, can constitute thelayer with randomly distributed continuous strands of the fibrousstructure that is the object of WO 03/060218, whose text is incorporatedin the present document by reference. More particularly, the mataccording to the invention can be incorporated into a multilayer complexhaving the following structure: mat according to the invention+layer ofstrands cut on one side of the mat according to the invention or mataccording to the invention+layer of cut strands on the two sides of saidmat (complexes with 2 or 3 layers). Thus it is possible to deposit ontothe moving belt a first layer of fibers (for example: strands cut, forexample, to a length of 12-100 mm), and then deposit the strands on thislayer to form the mat according to the invention, to proceed to theneedle punching according to the invention and thus link the two layersto each other by needle punching. One can also add a third layer (forexample: strands cut, for example, to a length of 12-100 mm) before theneedle punching according to the invention.

At the end of the manufacture of the mat, one can optionally proceed toa cutting of the edges of the ribbon of mat formed, because the edgesmay present a structure or density that is slightly different from thecentral part.

One would remain within the scope of the invention if one were toproceed in one of the following ways:

a) by binding the fibers of the mat with a water-soluble binder(example: a polyvinyl alcohol) before the needle punching and thenremoving the binder by dissolution in the water or in an aqueoussolution before the needle punching;

b) by binding the fibers of the mat with a water-soluble binder(example: a polyvinyl alcohol) before the needle punching, and thenremoving the binder by dissolution in water or in an aqueous solutionafter the binding;

c) by depositing or projecting the strands onto the film which itselfrests on a moving belt, and then winding the unbound blanket of strandsat the same time as the film (where the latter prevents the differentwound layers from mixing), for a possible intermediate storage, and thenunwinding the bilayer film/blanket by removing the film and placing theblanket back on a moving belt for the continuation of the methodaccording to the invention.

The mat obtained by the method according to the invention contains nobinder. It is symmetric with respect to a parallel plane and passesthrough its middle. It has sufficient cohesion to be wound into rollform and be unwound for use.

The invention leads notably to a needle-punched mat of continuousstrands or cut strands (preferably continuous strands) consisting ofmineral fiber (notably glass) that is optionally sized, and presentingno needle hole that is visible to the naked eye. This mat thus containsa maximum of mineral fiber to reinforce the composite as much aspossible, in the absence of polymer-based synthetic materials (PP,polyester, etc.) that are not reinforcing for the composite, except forpossible organic components of the sizing of the fibers. This mat isused advantageously to reinforce a composite in the closed-moldinjection method (RTM) or in the context of the SMC technology, or to beimpregnated directly with resin to make plates, particularly translucentplates.

The mat obtained by the method according to the invention can beintegrated in a prepreg sheet (SMC). The mat according to the inventionis then inserted continuously between two layers of thermosetting resinpaste. One unwinds and then integrates slowly said mat between twolayers of resin paste. In addition to the mat according to theinvention, it is not ruled out to add other reinforcement layers in theSMC, such as, for example, cut strands, notably glass strands. Forexample, one can proceed as follows:

-   -   horizontal unwinding of the mat according to the invention on a        layer of resin paste, then    -   projection onto the mat of cut strands, then    -   unwinding of the layer of resin paste onto the cut strands.

One can also place a layer of cut strands before unwinding the mataccording to the invention.

The SMC sheet can serve for the manufacture of a composite material bymolding the sheet via pressure on its principal faces, which leads to awidening of the sheet in the mold before the solidification of theresin. In the case where the mat has continuous strands, the cut SMCsheet has, before molding under pressure, preferably a surfacerepresenting 50-80% of the surface area of the mold (and thus of thesurface area of the final piece).

The fact that one does not use any chemical binder to produce the mataccording to the invention makes it possible to produce particularlytranslucent composites. The applicant has indeed observed that theabsence of binder notably improved the translucence of the finalcomposite. To produce such translucent composites, one can notably usethe method represented in FIG. 4 of WO2005/054559.

The solids content of a composition can be determined by evaporation inan oven at 110° C. for 12 h. Pure PVP has a solids content of 100% PEG400 mL has a solids content of 100%. For the person skilled in the art,in the case of silane, the reference is naturally to what remains of thesilane after the hydrolysis, and after evaporation of the water. Theperson skilled in the art also uses the term active matter. A174 silanehas a solids content of 82 wt %. Starting with 10 g of unhydrolyzedsilane, after hydrolyzing it and treating the hydrolysate in the oven at110° C. for 12 h, one finally collects 8.2 g of solids content. When onesays that the solids content of a sizing composition comprises 1-30%coupling agent, the person skilled in the art understands immediatelythat this solids content does not contain exactly the product assupplied by the manufacturer, but that it is a hydrolyzed residue ofthis product, which has then been dehydrated. Thus, one could sayequivalently that the solids content of the composition comprises 1-30wt % originating from a coupling agent.

EXAMPLES 1-5

In the following example, sizings according to the invention arecompared to a conventional sizing and to a sizing without PVP.

The conventional sizing (for Example 1) contained in its solids content(the latter representing 4% of the sizing composition):

-   -   5 wt % A174 silane    -   91 wt % Neoxyl film former    -   3.9 wt % Antarox lubricant.

The other sizing composition contained 1.3 wt % solids content, thelatter itself comprising 6.4 wt % of A174 silane and 50 ppm by weight ofan antifoaming agent (of trademark Agitan 295 marketed by MunzingChemie). The other ingredients of this solids content are indicated inthe second column of Table 1, and they are either PVP with aweight-average molecular weight of 900,000, or PEG 400 mL, or a mixtureas indicated of these two components. Thus, PVP 100% indicates that therest of the solids content, excluding silane and the antifoaming agent,consists of 100% PVP.

Using the continuous glass strand sized with these compositions, oneprepares mats with continuous strands by projection in a blanket on amoving belt. The projection was carried out using a device based on theprinciple of FIG. 4 of U.S. Pat. No. 3,969,171. The needle punching wascarried out according to FIG. 3 of WO2005/054559, with a punch densityof 3 punches per cm².

Composites were then produced by impregnation of the different mats withthe help of a thermosetting resin and according to the RTM procedure.

Table 1 below collects the results. A comparison is made between thedifferent sizings with regard to the behavior of the strand or of themat during different steps of the method, as well as to the level ofquality of the final composite. These are relative evaluations Thisbehavior was ranked −− (minimum rank) and ++ (maximum rank). Thefollowing behaviors were observed:

-   -   the behavior during the deposition of the continuous strand in a        blanket: in the case of Example 3, the deposition was difficult,        because the strand slipped too much on the wheels of the        projection device, so that the drawing of the fill was difficult        to control;    -   the behavior during the needle punching: two defects were        observed, breaking of strands in the case of Example 1, and        impossibility of needle punching in the case of Example 3; in        the latter case, the strand turned out to be too slippery, and        the strand returned too frequently when the needles came out of        the mat, which is equivalent to the near absence of needle        punching and the reason that the mat did not present sufficient        resistance;    -   the deformability by hand in the impregnation mold: it is        acceptable for all the examples; however, it is slightly        inferior in the case of Example 2;    -   the translucence of the final product.

{circle around (3)} {circle around (6)} {circle around (1)} Dépose{circle around (5)} Translucidité Ex {circle around (2)} en {circlearound (4)} Déformabilité Composite n° ensimage nappe Aiguilletage à lamain final 1 {circle around (7)} + + − − − − classique {circle around(8)} (cassures) 2 PVP: 100% + + + + + + + 3 PEG: 100% − − − + + {circlearound (9)} (ne tient pas) 4 PVP/PEG: + + + + + + + + 50/50 5PVP/PEG: + + + + + + + + 75/25 Key: {circle around (1)} Example No.{circle around (2)} Sizing {circle around (3)} Deposition in a blanket{circle around (4)} Needle punching {circle around (5)} Deformability byhand {circle around (6)} Translucence Final composite {circle around(7)} (conventional) {circle around (8)} (breaks) {circle around (9)}(does not hold)

1. Mat made of needle-punched strands comprising a strand made ofmineral glass that has been sized with a composition comprising water,where the solids content of said composition comprises 1-30 wt %coupling agent and 30-99 wt % polyvinylpyrrolidone.
 2. Mat according tothe preceding claim, characterized in that the strands are continuous.3. Mat according to one of the preceding claims, characterized in thatthe solids content of said composition comprises 2-10 wt % couplingagent.
 4. Mat according to one of the preceding claims, characterized inthat the solids content of said composition comprises 30-90 wt %polyvinylpyrrolidone.
 5. Composition according to any one of thepreceding claims, characterized in that its solids content comprises alubricant content of less than 79 wt %.
 6. Composition according to thepreceding claim, characterized in that the lubricant content is 5-70% inthe solids content.
 7. Mat according to the preceding claim,characterized in that the lubricant content is 20-70% in the solidscontent.
 8. Mat according to one of the preceding claims, characterizedin that the solids content of said composition comprises 5-500 ppm byweight of antifoaming agent.
 9. Mat according to one of the precedingclaims, characterized in that said composition contains no epoxy resin.10. Mat according to one of the preceding claims, characterized in thatthe solids content of said composition represents 0.5-10 wt % of saidcomposition.
 11. Mat according to the preceding claim, characterized inthat the solids content of said composition represents 0.8-6 wt % ofsaid composition.
 12. Mat according to the preceding claim,characterized in that the solids content of said composition represents0.8-2 wt % of said composition.
 13. Mat according to one of thepreceding claims, in the form of a roll.
 14. Method for the preparationof a mat of one of the preceding claims comprising a) the deposition orprojection of strands of mineral glass that are sized by the compositiononto a moving belt to form a blanket of said strands, which is driven bysaid belt, then b) the needle punching with barbed needles that passthrough said blanket and move in the direction of the blanket atsubstantially the same speed as the blanket when they pass through it,with a punch density ranging from 1 to 25 punches per cm².
 15. Methodfor the preparation of a composite material with thermosetting matrixcomprising the impregnation of a mat of one of the preceding mat claimswith a thermosetting resin.
 16. Method according to the preceding claim,characterized in that it is a method with injection into a closed mold(RTM).
 17. Method for the preparation of a prepreg sheet (SMC)comprising the continuous insertion of a mat of one of the preceding matclaims between two layers of thermosetting resin paste.
 18. Prepregsheet comprising a mat of one of the preceding mat claims and athermosetting resin.
 19. Method for the manufacture of a compositematerial by molding the sheet of the preceding claim by pressure on itsprincipal faces leading to a widening of the sheet before solidificationof the resin.
 20. Composite material with thermosetting matrix,reinforced by a mat of one of the preceding mat claims.